[PATCH v2 2/2] secretmem/gup: don't check if page is secretmem without reference
From: Mike Rapoport <rppt@kernel.org>
Date: 2021-04-20 13:17:05
Also in:
linux-arch, linux-arm-kernel, linux-fsdevel, linux-kselftest, linux-mm, linux-riscv, lkml
Subsystem:
memory management, memory management - gup (get user pages), the rest · Maintainers:
Andrew Morton, David Hildenbrand, Linus Torvalds
From: Mike Rapoport <redacted> The check in gup_pte_range() whether a page belongs to a secretmem mapping is performed before grabbing the page reference. To avoid potential race move the check after try_grab_compound_head(). Signed-off-by: Mike Rapoport <redacted> --- mm/gup.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c
index c3a17b189064..4b58c016e949 100644
--- a/mm/gup.c
+++ b/mm/gup.c@@ -2080,13 +2080,13 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, VM_BUG_ON(!pfn_valid(pte_pfn(pte))); page = pte_page(pte); - if (page_is_secretmem(page)) - goto pte_unmap; - head = try_grab_compound_head(page, 1, flags); if (!head) goto pte_unmap; + if (page_is_secretmem(page)) + goto pte_unmap; + if (unlikely(pte_val(pte) != pte_val(*ptep))) { put_compound_head(head, 1, flags); goto pte_unmap;
--
2.28.0